Safety switch for escalators



O. HOHNECKER SAFETY SWITCH FOR ESCALATORS May 5 .1953

Filed July 1, 1949 2 SETS-SHEET 1 (I tornegs 0. HOHNECKER SAFETY SWITCH FOR ESCALATORS May 5, 1953 .ZSl-IEETS-SHEETZ Filed July 1, 1949 w w r I 0 flow/mm Gttorneg Patented May 5, 1953 SAFETY SWITCH FOR ESCALATORS Otto Hohnecker, Toledo, Ohio, assignor to Haughton Elevator Company, Toledo, Ohio, a

corporation of Ohio Application July 1, 1949, Serial No. 102,535

. Claims. 1

r This invention relates to safety switches for escalators and, more particularly, to a safety switch system which automatically stops the operation of the escalator immediately upon the entry onto the escalator of a concentrated load greater than that which an escalator step is designed to carry or upon a jam at the escalator landing caused by an obstruction engaging between the moving steps and the landing structure, for example.

Escalators are constructed so that the stepcarts run on a continuous loop of track so designed as to maintain successive steps flat at the upper and lower landings of the escalators and to hold them in step or stairway relationship on the inclined portion of the escalators. In many instances it has been found that persons using escalators, particularly in factories and plants, either'through inadvertence or lack of knowledge, may attempt to transport on an escalator a concentrated load weighing much more than an escalator step is designed to carry. For example, escalators have been damaged by driving thereon such objects as factory fork-lift trucks or by usingv them for carrying heavy castings and other objects from floor to floor. When such a load is run onto the escalator it must enter at one of the landings where. the step treads lie in a plane.

Similar locally concentrated excessive loads (from an escalator operation and damage standpoint) occur whenevera foreign object is jammed between the leading edge of one of thesteps-and one of the comb plates which are located at the landings and beneath which the escalator step treads pass when disappearing to return out of sight to the other end of the escalator. Inv order to prevent the entry of large foreign objects into the interior of the machine and to minimize the possibility of injuring the fingers of children or of catching the shoes of other passengers, forexample, these comb plates are built to fit very closely to the surfaces of the step treads. Indeed, the comb plates and step treads usually have interdigitated ridges and fingers small enough in size to prevent the entry between the ridges of an object as slender as a common lead pencil. Quite frequently, however, smaller objects such as nails or a short piece of strong wire may enter the small spaces and jam the mechanism. The resulting effect upon the escalator is, of course, highly analogous .to an excessive deflection, since the mechanism may be locked up by the jammed object.

. It is, therefore, the. object of this invention to provide a safety switch which is positioned adjacent the normal path of travel of the escalator stepcarts and which, upon excessive loading of any of the steps at either of the landings, or upon jamming of any of the step treads by foreign objects engaging between the step treads and the comb plates will be actuated to disable the escalator driving machinery thereby to prevent damage to the escalator machinery.

It is another object of this invention to provide a control circuit for an escalator driving motor which will disable the motor immediately upon excessive misalignment of any one of the continuous flight of escalator steps at either of the landings.

More specific objects and advantages will be apparent from the drawings, in which:

Figure I is a perspective view of a modern escalator illustrating its general organization.

Figure II is an enlarged Vertical, sectional view passing through approximately the longitudinal median of the escalator shown in Figure I and illustrating in particular the general construction of the escalator at a lower landing.

Figure III is a vertical sectional view somewhat schematical in nature and including a wiring circuit, the mechanical portions of the figure being taken substantially on the line III-III of Figure II.

Figure IV is a fragmentary greatly enlarged vertical sectional view of an electrical contact element and cooperating portion of a step cart as seen looking to the left from the line IIIIII of Figure II.

Figure V is a fragmentary view in elevation taken from the right side of Figure IV.

In general an escalator comprises, among numerous other parts, a flight of steps, each of which consists of a stepcart l having a grooved tread 2, a cross frame 3 and two pairs of supporting wheels 4 and 5. The wheels 4 are known as chain wheels because a pair of driving chains 6 are linked between the stepca-rts i at the axes of the wheels 5 and serve both to hold the carts in a continuous flight and to move the carts over the loop of track both on the visible flight of the escalator and on the return flight which is located beneath the escalator machinery. The chains 8 usually are engaged with sprocket wheels, in turn driven by a power source which usually is an electric motor of heavy capacity. (The driving motor, sprocket wheels, gearing, etc., are not shown in the drawings.) The stepcarts I run on two pairs of tracks i and ii. The stepcarts are so constructed and the wheels 4 and 5 so positioned relative to the treads 2 that by properly shaping the pairs of tracks I and 8 the position of the succeeding stepcarts and succeeding treads 2 relative to each other can constantly be maintained, as is shown in Figure II. At the landings of the escalator the tracks 8 are located at a level beneath that of the tracks I so that the treads 2 of the escalator stepcarts remain on a substantially horizontal plane. As the carts enter the inclined flight of the escalator the tracks I and 8 are curved toward each other so that they lie substantially on the same inclined plane and thus, since the chain wheels 4 are spaced a lesser distance beneath the treads 2 than the other wheels 5, the steps have the appearance of a standard stairway when travelling up the incline. At the upper landing of an escalator the tracks are correspondingly bent to flatten out the treads and again present a substantially horizontal landing.

Escalators also are equipped with moving handrails 9 which travel at substantially the same speed as the stepcarts and which run on the upper surfaces of generally vertical balustradings III. The balustradings I border the stepcarts I forming the sidewalls between which the passengers move when travelling on the escalator and serve to enclose the handrail moving machinery and other parts, not shown. At each of the landings an escalator is equipped with a comb plate II which has a plurality of downwardly extending fingers I2 that are so positioned as to slide through the corresponding grooves in the surfaces of the treads 2 thus preventing the entry of foreign objects between the treads and the comb plates II and, by snugly fitting, also eliminating the possibility of the fingers of children or other persons from being damaged if the person should fall and. his hand lie in such a position when the step passes beneath the comb plate.

Because of the relatively close tolerances required to permit the stepcarts and their grooved treads 2 to pass beneath the comb plates II an escalator machine must be constructed quite carefully. The horizontal level of the treads 2 of the stepcarts I at the landings is held to very close tolerances and thus it is possible to detect any objectionable change in the position of the step treads which would result from an excessive impact, localized loading or jamming thereof and to thereby disable the driving mechanism. The means by which this is achieved will now be described. At each end of each of the balustradings I0, i. e., adjacent the path of movement of the treads 2 at the landings, there is located an adjustable contact I3 (see Figure IV). Each of the contacts I3 is threaded through a non-conducting bracket I4 mounted inside the balustrading I0 and projects through an opening I5 in the balustrading just in line with the path of the outer edges of the treads 2 when the stepcarts are moving along a horizontal landing portion of the escalator. Each of the contacts I3 is adjustable within its bracket I4 to vary the clearance between the end of the contact I3 and the edges of the treads 2. As shown in the drawings this adjustment is made possible by a pair of lock nuts I6 engaged with the contact I3. Thus, after the position of the contact I3 has been set with respect to the edges of the step treads 2, it can be permanently positioned by tightening the nuts I6 in place against the bracket I4. The nuts I6 also serve to secure a contact washer I'I, each of which is connected to an electrical conductor I8.

In Figure III the four contacts I3 are schemat ically shown in their respective positions at the upper and lower landings of the escalator and are diagrammatically wired together in parallel with each other and in series with a relay coil I9 and the secondary low-voltage coil of a power transformer 20 and thence to ground. The entire series of stepcarts is electrically linked by virtue of the metallic chains 8 and is grounded to the escalator frame. The contacts I3 are insulated from the escalator frame by the use of a non-conducting material in the formation of the brackets I4. The relay I9 has a normally closed contact 2| which is a part of a motor control circuit. The motor control circuit also has a normally open contact 22 which can be used to shunt out the relay control contact 2| when desired.

When one of the stepcarts, at either of the landings of the escalator, is subjected to a localized load far in excess of that for which it is designed the result is to displace the step bodily or to tip the outer edges of the treads 2 upwardly as shown by the arrow in Figure IV. In either case the edge of the tread is immediately engaged with one of the contacts I3 located at the landing where the excessive load has been applied to the escalator. Contact between the step tread 2 and the contact I3 immediately energizes the coil I9 and opens the contact 2I disabling the motor and stopping the escalator. The excessive load can then be removed and if no damage has occurred, the escalator resumes operation.

It has been found, indeed, that the contacts I3 can be adjusted so close to the edges of the step treads 2 that the deflection caused by the jamming of one of the stepcarts against the comb plates when passing therebeneath will also defiect the stepcart to such an extent as to engage the contact and stop the escalator. Such an cecurrence can be best understood by reference to Figure II and by considering that the stepcarts are moving to the left in that figure, i. e., that the figure illustrates the lower landing of a descending escalator. If then, for example, an object too large to pass through were to gain entrance into the space between the left or leading edge of one of the stepcarts and the right or lowermost edge of the comb plate II or its teeth I2, the tremendous forces immediately would distort the entire structure sufliciently to engage some part of the step with one of the contacts I3. Thus the contacts positioned adjacent the path of travel of the edges of the step treads at the landings where excessive loads might be placed upon the machine and where the step treads must pass beneath the closely fitting comb plates, reduce damage to the escalator machine and tend to prevent injury to passengers caused by the occurrences discussed.

The embodiment of the invention which has been disclosed is but illustrative of the form and shape of the contacts which might be employed and shows such contacts in preferred positions relative to the escalator steps and their paths of movement. Changes of size, of shape and position may all be made within the spirit and scope of the following claims.

Having described the invention, I claim:

1. In a safety control for an escalator having a continuous flight of step carts that move between fioors on an incline and along horizontal planes at floor level landings and having power means subject to a control circuit for driving the step carts, in combination, a relay having contacts included in the control circuit for the power means, said contacts being arranged so that the control circuit is operative when the relay is deenergized, and a control circuit for the relay that includes in series a source of power, step carts, and a contact member firmly mounted adjacent the path of the edges of the step carts and adapted to contact the edge of a cart straying from its intended path.

2. A safety control according to claim 1 in which the contact member has a portion vertically above the edge of the step cart to contact the edge of a vertically displaced step. cart and a portion laterally adjacent the edge of the step cart to contact the side of a laterally displaced step cart,

3. A safety control according to claim 2 having at least a pair of contact members connected in parallel in the relay control circuit and each pair being disposed with one contact on each side of the path of the step carts.

4. A safety control according to claim 1 in References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,645,619 Olson Oct. 18, 1927 1,832,204 Healy Nov. 17, 1931 2,030,103 Dunlop Feb. 11, 1936 2,109,210 Dunlop Feb. 22, 1938 2,345,415 Nagy, Jr. Mar. 28, 1944 

